IMO 1978 LL GBR21
A circle touches the sides AB, BC, CD, DA of a square at
IMO 1978 LL GBR21
Origin: GBR
Problem
A circle touches the sides AB, BC, CD, DA of a square at points K, L, M, N respectively, and BU, KV are parallel lines such that U is on DM and V on DN. Prove that UV touches the circle.